We prove a quantum ergodic restriction theorem for the Cauchy data of a sequence of quantum ergodic eigenfunctions on a hypersurface \(H\) of a Riemannian manifold \((M, g)\). The technique of proof is to use a Rellich type identity to relate quantum ergodicity of Cauchy data on \(H\) to quantum ergodicity of eigenfunctions on the global manifold \(M\). This has the interesting consequence that if the eigenfunctions are quantum unique ergodic on the global manifold \(M\), then the Cauchy data is automatically quantum unique ergodic on \(H\) with respect to operators whose symbols vanish to order one on the glancing set of unit tangential directions to \(H\).